In these years, the market of keyboardless devices that include no physical keyboards, such as smartphones, slate personal computers (PCs), and tablet devices including iPads (registered trademark), is rapidly expanding. In a keyboardless device, characters are input using a software keyboard as a character input interface. The types of software keyboards include ones in which touch panels are used and ones in which cameras, lasers, or the like are used.
A software keyboard that uses a touch panel displays an image of a keyboard on a touch panel display. The software keyboard then realizes input of a character by detecting a position at which a user has touched the touch panel.
As a software keyboard that uses a camera, a virtual keyboard that uses a camera for capturing an image of an operator's fingers from above and a camera for capturing an image of the operator's fingers from forward is known. For example, such a virtual keyboard is disclosed in Japanese Laid-open Patent Publication No. 2003-288156. The virtual keyboard captures images of the operator's fingers arranged in a plane or the like using the two cameras. The virtual keyboard then compares the position of the operator's finger with reference positions in a Z direction of three-dimensional coordinate axes represented by X, Y, and Z axes, and refers to positional information regarding virtual keys in an XY plane, in order to detect a virtual key intended by the operator.
In addition, unlike a hardware keyboard, a software keyboard can change the arrangement and the sizes of the keys and the like by changing the recognition ranges of the keys. For example, a technology is known in which a keyboard apparatus that uses a touch panel detects an erroneous input of a key by a user on the touch panel and adjusts the input reception range of an arbitrary key in accordance with a result of the detection. For example, such a technology is disclosed in Japanese Laid-open Patent Publication No. 2000-66817.
Upon detecting an input of a correction key such as Delete or Back Space, the keyboard apparatus performs learning using data such as a key code, input coordinates, and displacement from a target key. The keyboard apparatus then adjusts the input reception range of touch of a key on the touch panel.